The described apparatus is used to generate a visual color display from a stereo input and more specifically, generates a standard color television NTSC composite video signal for producing said display.
Numerous attempts have been made to produce displays in color or in black and white, from audio in either monoaural or stereo form. Some, like the apparatus for the Visual Aesthetic Display of Sound, by Weintraub, U.S. Pat. No. 3,604,852, couple the low, medium and high frequencies of monoaural sound to the three color beams, resulting in a display where color is a function of audio frequency. The lumping of all frequencies into low, medium and high bands severely reduces the amount of data available at the display so that the resultant display is not a reasonable analog of the original sound.
The Frequency Spectrum Analyzer With Displayable Colored Shiftable Frequency Spectrogram, by Miura, U.S. Pat. No. 3,581,192, uses a large number of audio filters and thus preserves a greater amount of real time data. The filter outputs are digitized, stored, multiplexed and applied to a color displaying device. On the resultant display, each display location is a function of time and frequency, and the color of each display point is a function of the intensity of the corresponding frequency. The resultant display is of use as a laboratory instrument, but does not necessarily produce a pleasing display, and has no provision for a stereo input.
There is a need, in the entertainment field for apparatus to display stereo in color where the display uses a significant amount of the data received from the audio lines, where the display is pleasing in appearance, where the operator has the option of choosing from a variety of displays, and where the apparatus can be produced at a reasonable cost.